#!/usr/bin/env python
"""
Scan networks for snmp hosts and add them to LibreNMS

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.

@package    LibreNMS
@link       http://librenms.org
@copyright  2017 Tony Murray
@author     Tony Murray <murraytony@gmail.com>
"""

from __future__ import print_function
from __future__ import unicode_literals

import argparse
from argparse import RawTextHelpFormatter
import json
from collections import namedtuple
from multiprocessing import Pool
from os import path, chdir
from socket import gethostbyname, gethostbyaddr, herror, gaierror
from subprocess import check_output, CalledProcessError
from sys import stdout
from time import time

try:
    from ipaddress import ip_network, ip_address
except:
    print('Could not import ipaddress module.  Please install python-ipaddress or use python3 to run this script')
    print('Debian/Ubuntu: apt install python-ipaddress')
    print('RHEL/CentOS: yum install python-ipaddress')
    exit(2)

Result = namedtuple('Result', ['ip', 'hostname', 'outcome', 'output'])


class Outcome:
    UNDEFINED = 0
    ADDED = 1
    UNPINGABLE = 2
    KNOWN = 3
    FAILED = 4
    EXCLUDED = 5
    TERMINATED = 6


VERBOSE_LEVEL = 0
THREADS = 32
CONFIG = {}
EXCLUDED_NETS = []
start_time = time()
stats = {
    'count': 0,
    Outcome.ADDED: 0,
    Outcome.UNPINGABLE: 0,
    Outcome.KNOWN: 0,
    Outcome.FAILED: 0,
    Outcome.EXCLUDED: 0,
    Outcome.TERMINATED: 0
}


def debug(message, level=2):
    if level <= VERBOSE_LEVEL:
        print(message)


def get_outcome_symbol(outcome):
    return {
        Outcome.UNDEFINED: '?',  # should not occur
        Outcome.ADDED: '+',
        Outcome.UNPINGABLE: '.',
        Outcome.KNOWN: '*',
        Outcome.FAILED: '-',
        Outcome.TERMINATED: ''
    }[outcome]


def handle_result(data):
    if VERBOSE_LEVEL > 0:
        print('Scanned \033[1m{}\033[0m {}'.format(
            ("{} ({})".format(data.hostname, data.ip) if data.hostname else data.ip), data.output))
    else:
        print(get_outcome_symbol(data.outcome), end='')
        stdout.flush()

    stats['count'] += 0 if data.outcome == Outcome.TERMINATED else 1
    stats[data.outcome] += 1


def check_ip_excluded(ip):
    for net in EXCLUDED_NETS:
        if ip in net:
            debug("\033[91m{} excluded by autodiscovery.nets-exclude\033[0m".format(ip), 1)
            stats[Outcome.EXCLUDED] += 1
            return True
    return False


def scan_host(ip):
    hostname = None

    try:
        try:
            # attempt to convert IP to hostname, if anything goes wrong, just use the IP
            tmp = gethostbyaddr(ip)[0]
            if gethostbyname(tmp) == ip:  # check that forward resolves
                hostname = tmp
        except (herror, gaierror):
            pass

        try:
            arguments = ['/usr/bin/env', 'php', 'addhost.php', hostname or ip]
            if args.ping:
                arguments.insert(3, args.ping)
            add_output = check_output(arguments)
            return Result(ip, hostname, Outcome.ADDED, add_output)
        except CalledProcessError as err:
            output = err.output.decode().rstrip()
            if err.returncode == 2:
                if 'Could not ping' in output:
                    return Result(ip, hostname, Outcome.UNPINGABLE, output)
                else:
                    return Result(ip, hostname, Outcome.FAILED, output)
            elif err.returncode == 3:
                return Result(ip, hostname, Outcome.KNOWN, output)
    except KeyboardInterrupt:
        return Result(ip, hostname, Outcome.TERMINATED, 'Terminated')

    return Result(ip, hostname, Outcome.UNDEFINED, output)


if __name__ == '__main__':
    ###################
    # Parse arguments #
    ###################
    parser = argparse.ArgumentParser(description='Scan network for snmp hosts and add them to LibreNMS.', formatter_class=RawTextHelpFormatter)
    parser.add_argument('network', action='append', nargs='*', type=str, help="""CIDR noted IP-Range to scan. Can be specified multiple times
This argument is only required if $config['nets'] is not set
Example: 192.168.0.0/24
Example: 192.168.0.0/31 will be treated as an RFC3021 p-t-p network with two addresses, 192.168.0.0 and 192.168.0.1
Example: 192.168.0.1/32 will be treated as a single host address""")
    parser.add_argument('-P', '--ping', action='store_const', const="-b", default="", help="""Add the device as an ICMP only device if it replies to ping but not SNMP.
Example: """ + __file__ + """ -P 192.168.0.0/24""")
    parser.add_argument('-t', dest='threads', type=int,
                        help="How many IPs to scan at a time.  More will increase the scan speed," +
                             " but could overload your system. Default: {}".format(THREADS))
    parser.add_argument('-l', '--legend', action='store_true', help="Print the legend.")
    parser.add_argument('-v', '--verbose', action='count',
                        help="Show debug output. Specifying multiple times increases the verbosity.")

    # compatibility arguments
    parser.add_argument('-r', dest='network', action='append', help=argparse.SUPPRESS)
    parser.add_argument('-d', '-i', dest='verbose', action='count', help=argparse.SUPPRESS)
    parser.add_argument('-n', action='store_true', help=argparse.SUPPRESS)
    parser.add_argument('-b', action='store_true', help=argparse.SUPPRESS)

    args = parser.parse_args()

    VERBOSE_LEVEL = args.verbose or VERBOSE_LEVEL
    THREADS = args.threads or THREADS

    # Import LibreNMS config
    install_dir = path.dirname(path.realpath(__file__))
    chdir(install_dir)
    try:
        CONFIG = json.loads(check_output(['/usr/bin/env', 'php', 'config_to_json.php']).decode())
    except CalledProcessError as e:
        parser.error("Could not execute: {}\n{}".format(' '.join(e.cmd), e.output.decode().rstrip()))
        exit(2)

    #######################
    # Build network lists #
    #######################

    # fix argparse awkwardness
    netargs = []
    for a in args.network:
        if type(a) is list:
            netargs += a
        else:
            netargs.append(a)

    # make sure we have something to scan
    if not CONFIG.get('nets', []) and not netargs:
        parser.error('$config[\'nets\'] is not set in config.php, you must specify a network to scan')

    # check for valid networks
    networks = []
    for net in (netargs if netargs else CONFIG.get('nets', [])):
        try:
            networks.append(ip_network(u'%s' % net, True))
            debug('Network parsed: {}'.format(net), 2)
        except ValueError as e:
            parser.error('Invalid network format {}'.format(e))

    for net in CONFIG.get('autodiscovery', {}).get('nets-exclude', {}):
        try:
            EXCLUDED_NETS.append(ip_network(net, True))
            debug('Excluded network: {}'.format(net), 2)
        except ValueError as e:
            parser.error('Invalid excluded network format {}, check your config.php'.format(e))

    #################
    # Scan networks #
    #################
    debug('SNMP settings from config.php: {}'.format(CONFIG.get('snmp', {})), 2)

    if args.legend and not VERBOSE_LEVEL:
        print('Legend:\n+  Added device\n*  Known device\n-  Failed to add device\n.  Ping failed\n')

    print('Scanning IPs:')

    pool = Pool(processes=THREADS)

    try:
        for network in networks:
            if network.num_addresses == 1:
                ips = [ip_address(network.network_address)]
            else:
                ips = network.hosts()

            for ip in ips:
                if not check_ip_excluded(ip):
                    pool.apply_async(scan_host, (str(ip),), callback=handle_result)

        pool.close()
        pool.join()
    except KeyboardInterrupt:
        pool.terminate()

    if VERBOSE_LEVEL == 0:
        print("\n")

    base = 'Scanned {} IPs: {} known devices, added {} devices, failed to add {} devices'
    summary = base.format(stats['count'], stats[Outcome.KNOWN], stats[Outcome.ADDED], stats[Outcome.FAILED])
    if stats[Outcome.EXCLUDED]:
        summary += ', {} ips excluded by config'.format(stats[Outcome.EXCLUDED])
    print(summary)
    print('Runtime: {:.2f} seconds'.format(time() - start_time))
